My U.S. Pat. No. 3,561,494 describes a hollow steel-lined castable porous ceramic tube which has been widely adopted for supporting molten metal samplers during their immersion into the melt bath. For example, these samplers may take the forms shown in my U.S. Pat. Nos. 3,457,790, 3,452,602 or 3,686,949. The formation of pin samples and disc samples in glass-tube pin sample molds and in mating chill-block disc molds, which may be combined with glass-tube pin molds, in conjunction with closed, baffled or compartmented de-oxidizing chambers forms the subject matter of William J. Collins' U.S. Pat. Nos. 3,415,124, 3,415,125 and 3,656,350. The use of continuous vacuum sources for drawing molten metal into the chill mold is proposed in U.S. Pat. No. 2,515,060, and intermittent or plunger actuated vacuum samplers disclosed in U.S. Pat. No. 2,970,350 and 3,309,928. An evacuated sampler is disclosed in U.S. Pat. No. 3,357,250.
For various reasons, problems have been encountered with all of the types of samplers disclosed in these prior art patents. Vacuum samplers themselves are reasonably satisfactory, but the vacuum equipment necessary to obtain samples must be used in a dirty, hostile steel furance environment, and the solidifying droplets or spattered molten metal and deposited layers of oxides, gums and moisture from the condensed hot gases of the melt clog and obstruct the vacuum passages of the vacuum system after a very few uses. This requires expensive baffle traps which must be disassembled after a very few sampling operations and cleaned in order to recondition the sampling assembly.
For these reasons, the prior art sampling devices of the kinds disclosed in these prior art patents have not met with complete acceptance and commercial success. An unfilled demand exists for a reliable sampler which will perform reproducible sampling operations and make dependable disc samples and pin samples, without bubbles or "pipe" inclusions of air or entrapped gasses in the sample itself, so that the sample may be quickly ground, polished, and subjected to metallurgical analysis without delay, and will provide a true representative sample of the molten metal under examination.
The use of two mating concave mold halves forming flat cylindrical pan-shaped chill molds, spaced apart by a slot of pre-determined width requires careful tolerances to release entrapped air sufficiently fast to permit a uniform sample to result when the sampler is used at particular depths or if the metal being sampled is at above-normal temperatures and thus more fluid and less viscous. When a combined pin-disc sample is desired, either the pin portion or the disc portion of the sample is likely to suffer from gas bubble inclusions, which interfere with the metallurgical analysis. U.S. Pat. No. 3,915,014 describes a sampler designed and manufactured by me, employed with a plastic entrance coating and a vacuum suction source, in order to collect satisfactory samples.
Prior standard sampling practice in obtaining samples in the steel industry for many years had been the use of spoons on long handles. The spoon is first "slagged", i.e., dipped into the hot slag at the surface of the melt. The hot slag freezes to the cold spoon, forming an insulating coating. The excess slag is poured off. The spoon is then dipped back into the furance deep enough to fill it with molten metal and then withdrawn. If the steel is "open" or unkilled, de-oxidant is added in wire form. Then the spoon contents are poured into mating halves of chill blocks. The procedure is: insulate, fill, kill and finally chill.
This has been proven to be the most accurate method of sampling over decades of steel making. "Immersion" samples allow for the extraction of samples at depths, or where conditions preclude the use of spoons, or where speed and time are important. The samplers described herein follow this procedure exactly; they insulate, fill, kill and chill in successive steps.